Reply to post: Wat?

Splice Machine bags $9m to fund RDBMS on Hadoop and Spark



>>Splice Machine RDBMS, a hybrid in-memory technology that incorporates >>Hadoop, ANSI SQL, ACID transaction

Unless they're counting an SSD as "in-memory" (stupid) or redefining "in-memory" to mean "has read caching" (mendacious) the only way to make DRAM based data engine ACID is to disallow writes.

D=Durability. A session cannot be allowed to StartTransaction until the previous Commit has a confirmed clean write to non-volatile storage. Doesn't matter if you replicate the transaction log to other nodes (e.g. MongoDB) to reduce single point failure risk, it doesn't qualify as ACID. Proper ACID systems go to great lengths to disable or force flush OS and storage controller write buffering for exactly this reason. That doesn't mean all (or even most) systems need ACID of course.

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